Scientists have drawn two conclusions when working to understand what attracts lionfish to island waters, Rotarians heard yesterday.

Gretchen Goodbody-Gringley, assistant scientist at Bermuda Institute of Ocean Sciences, has been studying the island’s reefs for ten years and said that water temperature and the common barber fish played an important role in the lionfish story.

Working with collaborators to understand the current lionfish invasion and its potential impact, the group has determined that the species prefers to congregate on deep reefs here in Bermuda and she identified one site, XL, as a “hot spot” for this “growing nuisance”.

The team surveyed five depths at 15 locations surrounding the island and theorised that the sites represent “spawning aggregations”.

This means that the juvenile lionfish, in a pattern similar to groupers, move to shallow waters and then migrate offshore to deeper water as they age, reproducing at depth.

The Harvard graduate also said they had also found a positive correlation between a large lionfish population in locations where there was “a lot of food and a diverse species group of food”.

Comparing the coral reef to a buffet at a Vegas hotel, she said that the resort that attracted the most variety would naturally draw crowds.

With no known predators, the “voracious eaters” can reduce recruitment of other fishes — that is the number of fish surviving to enter the fishery — by 80 per cent. The highly reproductive fish can also produce 30,000 eggs every four days, which means they are able to “outcompete” Bermuda’s local fish species. She added that, of the prey fish, only one species correlates with the lionfish — the African Creole Fish or barber. Gut content analyses also proved that this was the predator’s preferred dish of choice.

Dr Goodbody-Gringley said that, though they first determined that the physical environment seemed not to be as much cause for the lionfish’s migration as the presence of the barber fish, she discovered a “shocking” correlation last week that confirmed lionfish prefer the cooler waters as they were “very nutrient rich”.

The cold water, she said, was high in plankton, thus higher in the plankton-eating barber fish.

She said they were hoping that a better understanding of the conditions that attracted lionfish, could facilitate in circumventing their growth. “If lionfish target sites where barbers are abundant, they could essentially wipe out the entire barber population,” she said, adding: “This is important because this an economically important species in Bermuda, so there could be major ramifications for our fisheries industry.”

She said the outcome was not hypothetical, citing lionfish in the Bahamas, one of the most heavily invaded regions, as a cautionary tale.

“If we look at how this will affect coral reef ecosystems, the projection is bleak. If overfishing continues and lionfish are left unchecked, we can expect a drastic deadline in all levels of the food web, from the top predators to the herbivorous fishes.

“If this were to happen, what we would be left with is a reef covered in algae and lionfish, and this is what we desperately want to avoid.”

She outlined the Bermuda Lionfish Taskforce’s key future objectives — to initiate a deep-culling control programme, to continue to monitor the lionfish population and its impact on prey fish, to engage recreational cullers at shallow depths and to continue work implemented by fisheries to develop lionfish specific traps.